Low-frequency alternating-current signaling system



Aug. 22, ms. M65299 L. ESPENSCHIED ET AL LOW FREQUENCY ALTERNA'TINGHCURRENT SIGNALING SYSTEM Filed Sept. 27, 1919 MIR 4 MF I INVENTOR.

BY ii -Wk e I? 9 ATRNEY Patented Aug. 21; 1923. I r l UNETE M T rerenr aria;

:tLoYn nsrnnsonrnn, orinoLnrs ann JQHN r. roonnxfor nnwronx, n. Y., assrenons T AMERICAN 'rnanrnonn nnnrntne-nnrn COMPANY, A eonronanew or nnwiYonx.

LOW-FREQUENCY .aL'rnnnarrne-onnnnnr SIGNALING-SYSTEM.

' Application filed September 27, 1919. Serial No. 326,939.

To all whomit may concern. end of the toll line to the other end by the Be it known that we, LLOYD ESPENSOHIED actuation of a ringing key in the operators and JOHN F. TooMnY, residing at Hollis cord circuit connected with the line and the and New York; in the counties of Queens signaling current is transmitted over the a and New York and State of New York, reline only while the ringing key remains opspectively, have invented certain Improveerated. In the automatic system of signalments in Low-Frequency'Alternating-Curing current istransmitted from one end of rent Signaling Systems, of which the followthe toll line to the other merely by inserting is a specification. V ing the plug of the operators cord circuit so This invention relates to transmission into the jack of the toll line, the ringing systems and more particularly to lines arcurrent being continuously transmitted over ranged for the multiplex transmission for the line until the operator at the distant end currents for different purposes. responds by connecting with the line. The

It isa general purpose of the invention connection of the distant operator with the 15 toprovide atran'smission system over which toll line automatically transmits signaling alternating currents may be used for signal current back over the toll line, and thereby ing or other purposes and may be transoperates supervisory means in the cord cirmitted over such a system simultaneously cuit of the first operator. Furthermore with currents used for telephonic purposes with the arrangements of this invention an 20 and without interference withsuch latter alternating signaling current may be emcurrents or the terminalarra-ngements proployed which may be transmitted through vided for such currents. Inorder to acrepeater apparatus in the line without pro- 7 complish this purpose,' there is applied to viding special equipment at the repeater the transmission line simultaneously with station to transmit such currents around 2.5 the telephone channel, a signaling channel the repeater apparatus. Another feature or channels employing alternating currents of the invention is that with such arrangeof various frequencies not included in the ments, signaling currents may be employed telephonic range'of frequencies. At the terwhich may be of such a nature that they niinal arrangements of the system is pro may be used to control filament circuits of so vided a path for the telephonic currents and repeaters in the line and to regulate their a path for the currents used for the signal output. The signaling current which may ing purposes, each path including selective be used with the arrangements of this inapparatus for preventing the transmission vention may also be used for transmitting thereover of currentsexcept those for which impulses for operating and controlling 35 it was designed. An arrangement of this switching mechanism for establishing concharacter whereby a low frequency carrier nections between toll lines and toll switchchannel may be employed for signaling or ing trunks or subscribers stations or such other: purposes, is particularly desirable as current may be used in conjunction with a it is suitable for use with many types of start-stop distributor for providing a com- 40 transmission lines such as for purposes of 111011 signaling path for a number of toll illustration on the physical 'or phantom ci'rlines. Other and further features and pur cuits of both two wire or four wire toll lines poses of the invention will appear from the or on lines over which direct currents'might description hereinafter given.

not be transmitted. "The arrangements of The'i'nvention may be more clearly underthe invention whereby a low frequency caiifr stood from the following description torier-channel may beemployed for signaling gethcr with the accompanying drawlng in y is furthermore desirable 'in that it may be thel igures 1, 2 and 3,0f whichare illusused both with toll linesemploying the so trated circuit diagrams of a preferred form,

called ring-down system of signaling and and a Modification of the invention.

on toll lines-employing the so called autoin the Figure l is illustrated a transmis-.

matic system of. signaling; In "the: ringsion line L terminating in the pack J. For

H down system of signaling over atoll line purposes of illustration, the transmission line signaling current is transmitted from one L has been shown as one over which the he .;pointed out. later.

circuit.

N. adapted to balance thesection of thering-down system of signaling is employed.

As both low frequency signaling currents and currents of telephonic frequency may be transmitted over the line L, there is pro- -Nos. 1,227,113 and 1,227,114, dated May 22, 1917, and is designed to readily allow the transinission' of a band of frequencies including telephonic frequencies, but which attenuates and practically e-Xtinguishes currents of all frequencies below the telephonic range; lVith such an arrangement the signaling currents coming in over the line L will be prevented from being transmitted to the telephonic apparatus associated with the jack J. Bridged across the transmission line Lisa circuit suitable for the transmission of thcincoming signaling currents; This circuit includes an arrangement of inductances and capacities such as F and F adapted tomake the circuit sharply resonant at the frequency of the signaling currents employed. Accordingly such a circuit will readily allow the transmission of the signaling currents coming in over the line L, but will prevent the incoming telephonic currents from being transmitted over said Included in ,the circuit is network line L and-in parallel therewith the filter apparatus F Included. in the signaling circuitis the three-winding transformer 3. Associated with one winding of said transformer is a path for the signaling currents coming in over the line L. This path ineludes an arrangement F of inductanccs and capacity so that the path will be sharply resonant to currents of the frequency used for signaling. Included in this path is the aniplifier-roctilier A and the relay-4r. The relay 4 controls the relay 5 which in turn, controls the signal lamp 6 at the jack J. lVhen' the automatic system oi signaling is employed. the relay lw may be 'used to controlsupervisory signaling apparatus in the cord circuit associatedwith jack J as will Associated with the sleeve contact of jack J are the relays 7 and 8. Relay 8 controls the application of sig-' 'naling current from source 9 t0 the midpoints oi the three-winding transformer 3'.- from. which it will in turn be transmitted out over the line L.

The operation of the arrangements illus- *trated inzFigure 1 is as follows: As has been formerly pointed out, the arrangements illustrated-inFigure linclude a toll line 'L on which the ring-down system of signaling is employed} Low frequency currents, such .as' signaling currents coming in over the line L from a distant station in response tothe actuation thereat of the operators ringing key will be prevented from being trans-- readily allow the transmission of these signaling currents as it is sharply tuned'by the device F tobe resonant to currents of this frequency. The signaling currents areamplified and rectified. to direct-current in the amplifier-rectifier vacuum tubeA and are transmitted through the windings ofgand actuate relay 4;. "The direct current relay 4 and the amplifier-rectifier'A.are provided for the following purposes. lVhen an alternating carrier current channel is superposed on the line L for purposes ofsignaling orother purposes it is necessary in order to prevent harmonics of this signaling current from interferingwith the carrier channel superposed on the line for other purposes,

such as telephonic, purposes,- to so limit the signaling current as .to render it impossible. to operate theusualtypeof alternating current relay directly from the signaling cur; rent transmitted over the line. Accordingly including the amplifier-rectifier A and the direct, current relay 4 makes possible to further. prevent interference between the carrier channels superposed on the line L, as such arrangements may be operated by a type of signaling current which will not interfere with the other carrier channels. Theoperation of relayt will close the folthe provisionofa signaling receiving circuit lowing circuit: from ground, armature and contact ot'relay 4, conductor 17, armature and right hand contact of relay 7,-conductor 18, winding of relay 5, to battery} and ground. Therelay 5will :be locked up over the following circuit: from ground and bat tery, winding of relay 5, left hand contact and armature of relay-5', conductor 19,contact and armature of relay 7,-toground. The operation of relay 5 closes'the following-circuit fromgrounch armature and contact of relay 5, conductor QOyfilament of signaling lamp 6. to batteryand ground. The, closing of this circuit will light the signal lamp- 6. As the circuit including conductors" 1 and 2 and the circuit including sharply resonant to these relatively low frequency signaling currents. thesecircuits will not allow thetransmission thereover of the conductors 15 and 16 are each tuned to be eration of the signal lamp 6.

incoming telephonic currents and accordingly such currents Wlll not affect the op- If it ,is desired to transmit signaling current out over the line L to signal the operator at the distant end the operator willconnect a cord circuitsuch as 50 shown in Figure 3 with jaclcJ and-will throw the ringing-key K in the cord circuit. This would close the following circuit: from 7 ground and battery .55, contact of key K,

lay l.

winding of relay 51, sleeve conductor of cord, over the sleeve contact of the plug of the cord, sleeve contact of jack J conductor 21, windings of rela T 7, conductor 22, winding of marginal relay 8, to ground. The battery 5] included in this last mentioned circuit by the operation of the ringing-key will have a suiiicientlyhigh voltage to operate the marginal relay 8. It is pointed out that the marginal relay 8 wasnot operated merely by Connecting the plug of'the cord circuitwitli jack J as the battery 53 normally connected to the sleeve conductor in' the cord being of lowervoltage than battery is not othigh enough voltage to operate the marginal relay 8. The operation of relay 8 connects a source 9 of signaling current to the conductors 10 and 11. ,This signaling current will be transmitted through the'transformer 12 and over the conductors 13 and 14 to the mid-points of threewindings transformer At such points, the signaling current will divide equally, one portion being transmitted through the network N and the otherportion being transmitted over conductors 1 and 2 and thence out over the line L. The currents transmittedout over the line L will operate'at the distant'station relaying and signaling 'Ineanssimilartd relays 4: and 5 and signal lamp 6. The currents transmitted through the network N and the current transmittedout o-verthe line L will be equal and opposite and will accordingly induce no current in the secondary winding of transformer 3 and will not affect the re- The arrangements illustrated in Figure 2 are substantially similar to the arrangements of Figure 1 and similar reference numerals in each figure indicate like parts. The toll line L of Fig. 2 is shown as atoll line on whichis used the so called automatic system of signaling- In Figure 2 there is provided an "additional filtering device F1 which is included in a bridge across the talking conductors of the line L. This filtering device is similar to the filter F5. Theafilter telephonic range. If such currents were applied to conductors '10 and 11 and thence transmitted over conductors 13 and 14: to the midpoints or" the windings of transformers 3, one portion of these currents, which would divide at these midpoints, would betransmitted over conductors 1 and 2 to the line L. The hillil'lOIllCSOf such currents being within the telephonic frequency range might not be efliciently attenuated by the filter F; and would be transmitted over the line L beyond this filter. However, the other portion of the signaling current which divided 'at' the midpoints of the windings of transformer 3 would be transmitted over conductors 23 and 24. The harmonics of such currents would be transmitted through the filter F and thence over conductors 23 and 24: to the line L at the contact points 24 and 25. At these points this last mentioned current would neutralize any of the signaling current which was transmitted through the filter F and the signaling currents would not be transmitted further over the line L. Furthermore the .relay 8 of Fig. 2 is not marginal. As the Fig. 2 is in other respectssimilar to Fig. 1, no further description thereof will be given.

The operation of the arrangements illustrated in Fig. 2 is as follows: It has been pointed out that the toll line illustrated in Fig. 2 is the type oftoll line with which the so-called automatic method of signaling is employed. If it is desired to transmit signaling current out over the line L the operator willins'ert the plug ot her cord cir cuit such as 50 into ack J and this action will close the following circuit: from ground and battery 53 in the sleeve conductor of the cord circuit winding of relay 51. sleeve con tact of plug of cord, sleeve contact of jack J, conductor 21, low resistance and highresistance windings of relay 7, conductor 22, winding of relay 8, to ground; "The relay 8 in the arrangements or" Fig. 2 notmarginal and accordingly upon the closing of this circuit both relays 7;an(l 8 will be op erated. The relay 51 is marginal and will not be operated at this time,'as the circuit includes the high resistance windingot relay 7. The operation of relay 8- will connect a source9 of signaling current to conductors 10 and 11. Signaling current will then be transmitted through transformer 12, over conductors 13 and 14:, windings of transformer 3 over conductors 1 and 2, and thence out over the line. L. Inother words signaling current may betransmitted out over line L merely by the insertion of the plug of the'operators cord circuit into jack J. In a similar manner when the operator at the distant end of line'L in response to this signaling current makes a connection line L. This [signaling current will be transmitted from line L, over.conductors 1, 2 and through transformer 3, .over conductors 15,16-to the vacuum bulb A. The incoming signaling currents will then be amplified and rectified by the vacuum bulhAand will operatethe direct current relay 4. As has been formerly pointed out the connection of the operators cord circuit plug with ack J served to operaterelay '7. Accordingly when the relay at operates in response to the incoming signaling currents the circuit through the sleeve of the operators cord will now be completed as follows: from ground and battery 53, winding eta-relay 51 in th'esleeve conductor of cord sleeve contact of plug of cord, sleeve contact 01 jack J, conductor 21, low resistance .winding of relay 7, right handmake contact and armature of relay 7, conductor 17, contact and armature ofrelay ,4, to ground. As this circuit includes-only the low resistance winding of relay 7, the current Iflow over the circuit will be suflicientlyincreased to operate the marginal relay 51 in the sleeve conductor of the cord. This relay 5lmay control the operation of any suitable 3 signaling means such as lamp 52,01- may even control means for switching or for other purposes in the cordcircui-t.

It is understood that while reference has been made 7 to low v frequency currents ifor signaling purposes, that these curents may be employed for many purposes other than for merely controlling signaling devices. Furthermore while the arrangements of the invention have been illustrated gin connection with toll-lines arranged for eitherringdown signaling or automatic signaling, itis understood that the arrangements" of the in vention are capable of embodiment in many and widely varied forms without departing from the spirit of the invention as defined in the appended claims. 1

'What is claimed is: V r i 1.7 A transmission line upon which is superimposed a low frequency carrier cur rent and a high frequency carrier current, aiterininal station for said 'line .a filter in said line at said terminal station adapt-ed toireadily allow the transmission of-said 7 high frequency-current and to attenuate and practically extinguish said low frequency current, acircuittuned-to-beresonant to sa-id low frequency current bridged across said transmission line ion the incoming side of said filter, a network adapted to :balance a section of said-transmission lineincluded in saidtuned circuit, ;a second circuit, aithree winding transformer inductively relating said second circuit to'said last ,mentioned tuned circuit, a signaling means controlled by saidlast mentioned circuit, and means associated with said vtransmission line at said terminalstation whereby low frequency current may be applied to the-Inid-points of the primary-windings of said three {winding transformer.

2. A transmission line upon which is superimposed a low freque cy carriercurrent and a high frequency carrier current,

a terminal station for said line, a filter in" 'Sa-1Cl' line at sald terminalstationadapted to readily allow "the transmissionof' said high frequency current and to attenuate and practically extinguish said low frequency current, a circuit tuned to be resonant to said low frequency eurrentbridgedacross said transmission line on' the incoming side of said filter, alow frequencyreceiving circuit associated with vsaid tuned circuit, signaling means controlled by said low frequency Gil 1 cuit, a low frequency transmitting circuit associated with said tuned circuit,meansfor applying low frequency current tosaid low frequency transmitting,circu-it and thence over said tuned circuit and out over said transmission line, means for preventing said last mentioned currents from being transmitted over said low frequency receiving circuit, and means for preventing'harmonics of said last'mentioned currents from being 7 transmitted to said terminal station over said transmission llne.

3. A transmission line upon which-is superposed carrier currents for telephonic purposes and carrier currents of infra-telephonic frequency, a terminal station for said line, said line terminating in a jack at said terminal station, .a'selective circuit ,for said ,telephonic currents associated with said line at said terminal station, a selective circuit for ireceivtingsaid currentsof infra-telephonic frequency associated with said line V at said terminal station, ,means in said last mentioned selective circuit responsive to said currents of infra-telephonic frequency coming in over said line, a link circuit adapt-V ed to be associated with the jack of said line, at said'terminal station, a sleeve circuit associated with said link circuit and said transmission line, switching means in said link circuit controlling said sleeve circuit, and means controlled by said sleeve circuit whereby currents of infra-telephonic frequency may be transmittediout over said transmissionline,

4. A transmission line upon which is superposed carrier currents =for telephonic purposes and carrier currents of-lnfra-telephonic frequency, ta termlnal station for said line, said line terminating in a jack at said terminal station, aselective circuit for said telephonic currents associated'with said line at said terminal station,a selective circuit for receiving said currents of intratelephonic frequency associated with-said line at said terminal station, responsive means in said last-mentioned selective circuit responsive to said currents of infra telephonic frequency coming in over said line, a link circuit adapted to be associated with the jack of said line at said terminal station a sleeve circuit associated with said link circuit and said line, said sleeve circuit being closed upon the connection of said link circuit with said jack, means controlled by the closing of said sleeve circuit for transmitting currents of infra-telephonic frequency out over said transmission link, su-

V pervisory signaling means in said link circuit and associated with said sleeve circuit, and means controlled by said responsive means in said second mentioned selectlve circuit whereby the resistance of said sleeve 15 circuit may be varied so as to operate said supervisory signaling means.

In testimony whereof, We have signed our names to this specification this 25th day of September 1919.

LLOYD ESPENSCHIED. JOHN F. TOOMEY. 

